Hello
what I have read the Russians liked P-39's radio, so I doubt that it was usual to remove it. And I have never read before that the two .5 mgs in the nose were removed. On the other hand wing mgs were rather often removed to lighten the plane and maybe also to improve the rate of roll. This can be seen from many photos. In about ½ of the photos on Russian P-39s which I have seen and from which it have been possible to see the area were wing guns are/should be the wing mgs were removed.
A good interview of a Soviet ex-P-39 pilot can be seen here
http://lend-lease.airforce.ru/englis...ikov/part3.htm
Juha